A great many different demands are made of absorbent articles, such as a sanitary towel, an incontinence pad, a nappy or the like, which are not easy to satisfy simultaneously. A fundamental requirement is that the article, for example a sanitary towel, should be capable of catching and absorbing bodily fluid discharged from the wearer. Conventional sanitary towels in sizes intended for heavy flows of menstrual fluid have been of thick and relatively wide design. Sanitary towels of this type are described in, for example, U.S. Pat. No. 3,294,091. Thick and relatively wide sanitary towels of this type theoretically have great absorption capacity but in practice, when the sanitary towel is subjected to compression forces when squeezed together between the thighs of the wearer, much of the take-up capacity and absorption capacity is lost. The sanitary towel is squeezed together into an arbitrary rope-like shape which frequently does not offer a sufficiently large receiving surface for the menstrual fluid discharged, and leakage occurs in the case of heavy flows of menstrual fluid. The sanitary towel can also be pressed together between the thighs of the wearer in such a manner that the side edges of the sanitary towel and the liquid-tight layer are folded in over the liquid-permeable surface and in this way reduce the size of the liquid-receiving surface available.
Sanitary towels are intended to be positioned inside a pair of briefs, the design of which may vary. In this connection, sanitary towels can be positioned incorrectly inside the briefs. There is therefore a risk of the sanitary towel being, by mistake, positioned too far forward or too far back or displaced slightly in the lateral direction; and therefore, the absorption capacity and receiving surface of the entire sanitary towel may not be optimally utilized.
Conventional sanitary towels are generally retained in the briefs of the wearer by means of pressure-sensitive adhesive or friction coatings. The sanitary towel is fitted by the towel being put in place in the briefs, after which the latter are pulled up into position. When fitting the article inside the briefs, however, it is difficult to achieve a positioning which is optimum in relation to the body of the wearer. Use is usually made of the crotch portion of the briefs in order to determine where the sanitary towel should be positioned. As sanitary towels are manufactured in a great many sizes and models, the position and design of the crotch portion provide a particularly uncertain indication of where in the briefs a sanitary towel is to be positioned, and the functioning of the sanitary towel during use is consequently not always as desired.
Another cause of leakage occurring past sanitary towels attached inside the briefs of the wearer is that the sanitary towel moves together with the briefs instead of following the body movements of the wearer. This means that even a sanitary towel which was from the outset positioned correctly in the briefs in relation to the body can be pulled out of this position by the briefs.
In order to attempt to reduce leakage arising as a result of the sanitary towel being pressed together between the legs of the wearer, it has become usual to provide the sanitary towels with special attachment flaps. It is known from, for example, SE 455 668, U.S. Pat. No. 4,285,343, EP 0 130 848, EP 0 134 086 and U.S Pat. No. 4,608,047 to provide sanitary towels with flexible side flaps or wings projecting from the longitudinal side edges. These are intended to be folded around the edge portions of the briefs of the wearer when the sanitary towel is put on, and to be attached to the outside of the briefs. The side flaps themselves constitute protection against side edge leakage and soiling of the briefs. Moreover, deformation of the absorption body of the sanitary towel is counteracted by virtue of the fact that the sanitary towel is anchored at the leg edges of the briefs and is held extended between these during use.
However, a considerable disadvantage of providing absorbent articles with such attachment flaps is that many wearers find it embarrassing that the attachment flaps are visible on the outside of the briefs. This also means that absorbent articles with such attachment flaps cannot be used when, for example, the wearer is wearing a swimsuit.
Another disadvantage of the attachment flaps is that they are relatively difficult to handle and require many manual operations in order to be fitted correctly around the leg edges of the briefs. Furthermore, especially in the case of attachment flaps which extend quite a long way along the side edges of a sanitary towel, it can be virtually impossible to fold the attachment flaps around the curved leg edges of the briefs without chafing and unattractive creases in the attachment flaps occurring.
A further problem of sanitary towels with attachment flaps is that the functioning of the attachment flaps or wings depends on the design of the briefs. It goes without saying that a sanitary towel with attachment flaps interacts differently with briefs with a wide crotch compared with briefs with a very narrow crotch.
Attachment flaps or wings on sanitary towels protect the leg edges of the briefs from soiling but, for at least the reasons discussed above, are far from being an entirely satisfactory solution.
In order to improve leakproofness, EP 0 067 465 has proposed manufacturing a two-part sanitary towel in which the two parts are interconnected only at their end portions. The lower part is fastened in the briefs of the wearer, and the upper part makes contact with the body of the wearer. The idea is that the parts will be able to move slightly in relation to one another during use. The mobility between the parts is, however, very limited, and the known sanitary towel is still dependent on the movements of the briefs. Furthermore, there is no guarantee that the upper part will be held in contact with the body of the wearer during use.
PCT/SE96/01061 describes another two-part absorbent article in which the two parts are movable in relation to one another. This known article also has limited mobility between the parts and is to a certain extent dependent on the movements of the briefs.
One way of attempting to reduce the risk of edge leakage caused by deformation of the sanitary towel during use is to provide the sanitary towel with a preshaped raised portion, what is known as a hump, which is intended to make contact with the genitals of the wearer during use of the sanitary towel. Discharged bodily fluid can in this way be caught as soon as it leaves the body of the wearer and be absorbed immediately into the article instead of running out over the surface of the latter. A raised portion also makes it easier for the wearer to position the article correctly in relation to the body. French patent publication FR-A-2 653 328 describes a sanitary towel with a hump in the form of a central, longitudinal, cylindrical raised portion.
A common way of creating a raised portion has been quite simply to build it up by arranging a greater quantity of absorption material within the area of the raised portion. As the absorption material used is in most cases what is known as cellulose fluff pulp, however, such a raised portion collapses and loses its shape when it is wetted. In order to produce a raised portion which is sufficiently large in the wet state as well, a raised portion consisting of cellulose fluff pulp must comprise so much absorption material that it is altogether too high, hard and uncomfortable to wear in the dry state.
It is also known to produce an article with a raised portion facing the wearer by positioning a shaping element on top of the absorbent core. The disadvantage is that this interferes with the liquid transport down to the absorbent, liquid-retaining absorption core and that leakage can occur because the shaping element does not have sufficient admission capacity or temporary retention capacity. The use of, for example, a foamed material in the raised portion has been proposed. However, it has proved difficult to produce a foamed structure with sufficiently open pores for good liquid admission into the latter at the same time as the material is to have such great retention capacity that liquid is not pressed out in the event of loading originating from the wearer, for example when the wearer sits down.
Another example of a raised portion is described in Swedish patent 507 798. Such a raised portion has a predictable shape, both before and during use, and also keeps its shape irrespective of the movements of the wearer and of the wetting to which it is subjected. The raised portion is anatomically designed, which means that it is relatively narrow in order to project in slightly between the labia of the wearer during use without causing discomfort for the wearer.
Although such a raised portion functions well for its purpose, it has been found that when the raised portion is exposed to large quantities of bodily fluid over a relatively short period of time, there is a risk that some of the liquid will run on the outside of the raised portion and flow out past the side edges of the absorbent article. Such leakage can occur, for example, when the wearer of a sanitary towel has been sitting or lying down for a relatively long period of time and then suddenly rises. This is because, when the wearer is sitting or lying down, a relatively large quantity of menstrual fluid accumulates in the vagina of the wearer. In the event of a sudden change in body position, the entire quantity of accumulated liquid may be discharged at once. A narrow raised portion of the type described in SE 507 798 does not then have a sufficiently large surface to be capable of receiving and absorbing the entire quantity of liquid at one time, for which reason such sudden liquid flows often result in leakage.
EP 0 335 252 and EP 0 335 253 have proposed providing an absorbent article with a deformation element. The deformation element is acted on by the transverse compressive forces between the thighs of a wearer. The purpose of the deformation element is to cause a portion of the article to bulge in the direction of the body of the wearer during use. It is impossible, however, to control or predict entirely the shape the article will adopt for each individual wearer. Moreover, it is not possible to ensure contact between the body of the wearer and the surface of the article, because the degree of bulging is determined entirely by how much the article is compressed in the transverse direction.
U.S. Pat. No. 4,804,380 describes an absorbent article which has a permanent three-dimensional shape. The article has one end portion of flat or concave shape and one end portion provided with a raised portion. The flat or concave end portion is intended to be positioned in front of the mons Veneris of the wearer, and the end portion comprising the raised portion is intended to fit in against the buttocks of the wearer. The three-dimensional design of the article is brought about by folding a fairly stiff absorption body. In order to make the raised portion permanent, the rear side of the article is provided with a glued surface in the end portion which is to have the raised portion. When the raised portion has been formed, it is maintained by means of the glue.
There are absorbent articles on the market which have a permanent, three-dimensional, boat-like shape and in which the outer shell consists of a moulded polymer foam.
A considerable disadvantage of permanent three-dimensional products is that it is difficult to pack a stiff three-dimensional product. Such products require a great deal of space for transport and sale, and it can be embarrassing for a wearer to carry around a sanitary towel or an incontinence pad when it is impossible to fold and therefore cannot be concealed in the hand or in the worst case will not even fit in a handbag.
EP 155 515 describes how an absorbent article, such as a sanitary towel, is provided with a bowl-shaped appearance by virtue of elastic being applied in a pretensioned state at the longitudinal side edges of the article. However, the use of such elastic complicates manufacture.
It is previously known to design plane absorbent articles which adopt a three-dimensional, essentially bowl-like shape when applied. An example of this is described in U.S. Pat. No. 4,655,759, which discloses an elongate sanitary towel consisting of a layer of absorbent material, a flexible liquid-tight outer layer and a liquid-permeable inner layer. The sanitary towel is provided with a pair of channels formed by stamping, the channels being located on both sides of a longitudinal centre axis and extending along a curved path over the absorption material layer. The two paths together form an hourglass-like shape positioned centrally over the towel. Before use, the sanitary towels are essentially plane but, when they are applied to the wearer, they are folded into a bowl-like shape, that is to say with liquid-stopping upright borders outside the channels. One disadvantage of this bowl-like construction is that the borders hold the central portion of the sanitary towel at a distance from the genitals of the wearer, and liquid discharged from the wearer does not flow directly into the absorbent article but can run on the surface, the risk then being obvious that liquid may find an undesirable transport path in the form of a small crease or the like and run straight out of the product in the lateral or longitudinal direction. Stamped channels in an absorption body also have the disadvantage that the liquid spread in the absorption layer is disrupted and that absorption material outside the channels is not utilized, which increases the risk of local oversaturation and attendant leakage from those parts of the absorption layer which are used.
Previously known sanitary towels and the various problems associated with them have in the main been discussed above. However, what has been said above also applies to incontinence pads. Nappies for children and adults also belong to the same problem area as far as fit in the crotch and take-up of liquid in an absorption body are concerned.
As emerged above, great efforts have been made over many years in order to attempt to solve all the problems associated with absorbent articles, such as sanitary towels. Although great improvements have been made, all the previously known solutions are associated with some disadvantages.